The present invention relates generally to irrigation systems and pertains, more specifically, to a rainfall responsive switch for discontinuing the supply of water in an irrigation system, such as a lawn sprinkling system, in response to the occurrence of rain at the irrigated area in order to conserve water and the energy employed to deliver the water to the irrigated area, as well as to prevent over-watering.
Irrigation systems of the type designed for watering lawns are in common use. It has been suggested that electronic controls be employed in such systems for discontinuing the sprinkling of water during periods of rain to thereby conserve water and energy, and to prevent over-watering. Thus, several patents to Sanner, namely, U.S. Pat. Nos. 3,500,844, 3,848,616, 3,915,185, 4,014,359 and 4,246,574, illustrate and describe a variety of control arrangements in which rain responsive switches are incorporated into control circuits for lawn sprinkler systems. While many of these rain responsive switches rely upon moisture absorption to effect operation, some of the above-enumerated patents recognize that instant switch activation and deactivation can be advantageous when combined with electronic circuit devices for better control, and disclose a planimetric switch designed for such instant response.
The present invention provides an improvement in the construction of a rainfall responsive switch of the type which is activated immediately upon the occurrence of rain and is deactivated when rainfall stops. As such, the present invention provides an improved switch construction which attains several objects and advantages, some of which may be summarized as follows: Enables rain water to pass through without substantial accumulation for immediate activation upon the onset of rain and deactivation as soon as the rain stops; allows ambient air to pass through, not only for venting to restore the switch to a deactivated state quickly, but for enabling an omnidirectional flow of air to remove any loose airborne debris which otherwise could impede such deactivation; provides a construction which is highly sensitive to rainfall and remains sensitive over longer service periods without the requirement for frequent maintenance and cleaning to attain long-term sensitivity; exhibits a construction which tends to maintain itself in working order, thereby reducing cleaning and maintenance requirements for long-term reliability; and provides a rugged construction which withstands exposure to ambient conditions for reliable operation over a long service life.